Thermostatic mixing faucet having improved stability

ABSTRACT

Two flow control ceramic discs ( 22  and  24 ) for a thermostatic valve ( 10 ) have ports ( 30, 32, 38  and  40 ) to adjust water flow from a closed to a full open position. Ceramic disc ( 24 ) has a contoured opening ( 38  and  40 ) that has a wide section ( 84 ) and a narrow section ( 85 ) that provide regulation fields with significant different capacities of flow rates.

TECHNICAL FIELD

The field of this invention relates to a thermostatically controlledmixing valve and more particularly to a thermostatic controlled mixingvalve with a volume control feature incorporated therein.

BACKGROUND OF THE DISCLOSURE

Mixing valves are well known and common in the plumbing field. Thesevalves provide a flow of mixed water from separate hot and cold watersupplies. Secondly, thermostatic control for handle mixer valves arewell known. One reason for thermostatic control is to eliminate constantreadjustment of the valve when the temperature of the hot water supplyfluctuates. The temperature of the hot water supply may varysubstantially. Furthermore, the pressure within the cold water line mayalso vary changing the proportions of hot and cold water flow andthereby fluctuating the temperature of the mixed water.

Known thermostatic valves have packaging problems and are oftensignificantly bulkier than standard mixing valves that do notincorporate the thermostatic regulation. This bulkiness is due to theflow path that has always been used for thermostatic faucets, namely thesupply inlets approach the centrally located thermostatic valve from aradially outer position.

When thermostatic valves are incorporated into mixer valves, the volumeor flow control valves may be installed either downstream or upstreamfrom the thermostatic valve element. When the flow is regulateddownstream of the thermostatic element within the mixed water flow,installation of non-return valves are needed in order to prevent thepossibility of communication between the hot water supply and the coldwater supply. When the flow control of the hot and cold water suppliesis upstream of the thermostatic valve before the water is mixed, thereturn valves are not needed. For this economic reason, mostthermostatic mixing valves have the volume control upstream of thethermostatic element.

However when the flow is regulated with respect to the hot and coldwater supplies, the thermostatic device is unable to maintain theconstant temperature due to the variations of the flow rates. It is wellknown that when hot and cold water supply pressures are approximatelyequal or with the hot supply pressure being only slightly lower than thecold water pressure, the difference in flow rate or variation betweenthe hot and cold water supplies is increased when the total flow isreduced and the rise in temperature can sometimes become significant. Onthe other hand, if the hot water supply pressure is substantially lowerthan the cold water supply pressure, as is often the case due theincreased corrosion of the hot water pipelines, the difference in theflow rate or variation of the flow rate between the hot and cold watersupplies is decreased as the total flow rate is reduced.

Contoured apertures in a pair of disc plate valves have been known tocontour the water flow profile between the hot and cold water supplies.However, these plate valves are set to move both rotatably andtranslationally with respect to each other to mechanically control boththe total flow rate and the temperature mix of the hot and cold water.

A thermostatic mixing valve has been developed that includes two inletsfor hot water and cold water, a mixing chamber, passages between theinlets and the mixing chamber, an outlet for the mixed water which runsfrom the mixing chamber, an expanding thermostatic element placed, atleast in part, within the outlet so that it will be in contact with themixed water. A slide valve is activated by the thermostatic element andacts on one or both of the inlet passages to maintain the mixed water ata constant temperature. The inlets are located in a central bodysituated inside the slide valve activated by the thermostatic element. Apair of valve plates crossed by passages for the water are positioned tocontrol total flow rate through the inlets for the hot water and coldwater without affecting the outlet for the mixed water. The valve platesare controlled by rotation of an external body or housing of thethermostatic mixing valve. A thermostatic mixing valve of this kind hasproved to be very advantageous, yet (like other types of thermostaticmixing valve) it can prove to be inconvenient in certain conditions.

If a thermostatic mixing valve, which is designed to be able to delivera determined rate of flow, supplies a device downstream which, due toits own high resistance only allows delivery of a much lower rate offlow, the fall in pressure at the inlet produced by the pair of valveplates is greatly reduced in comparison to the fall in pressure at theinlet produced by the downstream device and the pressure inside thethermostatic mixing valve is close to the pressure in the supply pipes.If a considerable difference in pressure then occurs between the hot andcold water supplies, for example because of the actuation of a devicewith high rate of flow that uses primarily hot or cold water upstreamfrom thermostatic valve, the valve will then be unstable and will startto oscillate, because of the cross-flow which occurs inside thethermostatic valve. The oscillation will cause malfunctioning andtemperature instability in the mixed water delivery downstream from thethermostatic valve. This situation may occur when a thermostatic mixingvalve is designed to supply a relatively high rate of flow, such as forexample 50 or 60 liters per minute at 3 bars but is used with a muchlower delivery rate, for example 9 liters per minute due to theresistance or restriction at the outlet on certain downstream devices.This situation occurs, for example, when the thermostatic mixing valveis installed to supply a bank with multiple outlets, each of which isequipped with its own on/off valve, and the user makes use of only oneoutlet. More generally, the situation occurs when the thermostaticmixing valve is capable of supplying many devices and only one or a fewof these devices are actually in operation at any given time.

In fact, the user could in theory prevent this instability by accurateregulation of the thermostatic mixing valve, so as create a resistanceat the inlet that proportional to the resistance at the outlet. However,this is not possible in practice, because well-known thermostatic mixingvalves do not offer sufficiently sensitive regulation at low rates offlow. Furthermore, since the rate of flow is limited at the outlet of adevice with high restriction or resistance, the user is not aware of theeffect of the regulation at the downstream device and is therefore notin a position to decide whether the regulation he has carried out isadequate to avoid the noted problem.

This problem which also occurs with other kinds of thermostatic mixers,has usually been remedied by installing a pressure controller in thesupply pipes upstream of the thermostatic mixing valve. This pressurecontroller, however, increases the size, complexity and expense of theinstallation and renders the device less reliable.

What is needed is a compact thermostatic valve that is easily assembledand controls the temperature of the mixed water output. What is alsoneeded is a thermostatic control built into a valve with flow controlthat provides proper thermostatic control at a wide range of flow rates.

SUMMARY OF THE DISCLOSURE

In accordance with an aspect of the invention, a thermostatic mixingvalve has a cold water inlet port and a hot water inlet port incommunication with a base having two supply ports. A handle body isrotatably mounted onto the base and is operably connected to a firstvalving surface with two inlet passages therethrough that are operablypositioned adjacent the two supply ports for controlling total flow rateinto the housing. A thermostat element is operably connected to a secondvalving surface to move the second valving surface between a first andsecond seat for controlling the relative flow from the first and secondinlet passages in response to the temperature of fluid in the mixingchamber.

The ports and the first valving surface are incorporated in twoconcentrically mounted plates that can be rotated with respect to eachother and provided with openings therethrough for the controlled passageof the fluid through the two plates. The opening in one of the valveplates which control the inlet pipes for hot water or cold water isconstructed so as to sub-divide the whole field of regulation determinedby the relative rotation of the plates into at least two successivefields. The first field of regulation is positioned adjacent to the shutoff position is and formed by a narrow section of the opening. Thesecond field of regulation is positioned and after the first is formedby a wide section of the opening. The first and second fields arepreferably inserted into both the hot water and cold water passages.

When the thermostatic mixing valve has to supply one or more devices,which provide a low flow rate, it is positioned into its first field ofregulation, which occurs as soon as the thermostatic mixing valve ismoved from its closed position. The narrow section of at least one ofthe inlet passage openings then causes a relatively marked fall inpressure, even in the presence of a low flow rate caused by highresistance at the outlet, and renders the thermostatic mixing valvepractically and advantageously stable to even significant differences inpressure between the supply pipes. When the thermostatic mixing valve isused to supply devices with large flow rates, the thermostatic valve ispositioned to its second field of regulation. The wide section of theinlet opening enables delivery of large flow rates. Under the condition,any differences in pressure between the hot and cold supply, even ifsignificant, do not cause temperature fluctuation problems.

It is desirable to provide an intermediate field of regulationinterposed between the two fields of regulation determined by the narrowand large sections in the openings respectively. The intermediatesection has a width which is intermediate between those of the other twofields of regulation.

It is also possible to use inlet passage apertures for both valve plateswhich have special shapes. Preferably, one of the valve plates (forexample the fixed one) should have inlet openings which have theconventional shape of an elongated curved slot. The other valve plate(for example the moveable one) should have inlet openings shaped withdifferent passage sections to determine the two or more distinct fieldsof regulation of the thermostatic mixing valve.

In one embodiment of the invention, the inlet openings of one of thevalve plates are in the shape of elongated slots. At least one of thesehas a first section of reduced width, a second section of enlarged widthand, optionally, an intermediate section of width which is intermediatebetween the widths of the first and second sections. In anotherembodiment of the invention, the inlet opening of one of the valveplates has large, uniform width. At least one of these openings has onlya first section that extends fully through the plate. A second sectionhas a limited depth and does not fully pass through the valve plate. Anoptional intermediate section of greater depth than that of the secondsection can be provided between the first section and the secondsection.

In another embodiment of the invention the openings include sectionsthat fully passes through the plate and at least one section of limiteddepth that does not fully pass through the valve plate which has anarrower width and is adjacent a narrow slot section.

In accordance with another aspect of the invention, visible indicatorson parts of the thermostatic mixing valves inform the user which fieldof regulation the thermostatic mixing valve is operating in at any giventime. In addition or alternatively for the visible indicators, deviceswith an elastic or detest release, can give the user a tactile warningof passage of the thermostatic mixing valve from one to another field ofregulation. This device is useful in making it very easy for the user toidentify the field of regulation of the thermostatic mixing valve whichis most suitable.

In this fashion, a compact thermostatic cartridge is provided. Thecartridge can be housed in a mixer valve flow regulator with volume orflow rate control disc plates that have contoured apertures to assureset flow ratios between the hot and cold water supplies independent ofthe total flow rate through the disc plates.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference now is made to the accompanying drawings in which:

FIG. 1 is a side-segmented view of a thermostatic mixing valve inaccordance with one embodiment of the invention;

FIG. 2 is a top perspective view of a fixed plate for the flow rateregulation shown in FIG. 1;

FIG. 3 is a top perspective view of the movable plate shown in FIG. 1;

FIGS. 4a and 4 b illustrate the movable and fixed valve plates in theirrelative closed positions;

FIGS. 5a and 6 a illustrate the movable valve plate in two differentoperating positions.

FIGS. 5b and 6 b illustrate the relative position of the fixed plate andmovable valve plate positioned behind the fixed plate;

FIG. 7 illustrates a second embodiment of the movable plate;

FIG. 8 is a bottom perspective view of a third embodiment of the movablevalve plate;

FIG. 9 is a segmented view showing the movable plate in the fully openposition with respect to the fixed plate;

FIG. 10 is a view similar to FIG. 8 illustrating a fourth embodiment;

FIG. 11 is a view similar to FIG. 9 for the fourth embodiment;

FIG. 12 is a view similar to FIG. 8 illustrating a fifth embodiment;

FIG. 13-16 illustrate other embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a thermostatic mixing valve 10 includes a rotatablebody 12 that is rotatably mounted in piping fixture or other suitablepiping fixture 14. The piping fixture 14 includes a cold water supply 16and hot water supply 18. The handle body 12 is rotatably mounted to afaucet base 17 that is affixed within the fixture 14. The base 17 has apositioning lug 19 seated in a lug receiving hole in fixture 14. Themixing valve includes a flow rate control valve 20 that includes twoceramic disc plates 22 and 24. Fixed ceramic disc plate 22 is mounted inbase 17. Rotatable ceramic disc plate 24 is mounted to a bottom of acartridge assembly 25. The cartridge assembly 25 includes a thermostaticcontrolled second valve 26 mounted downstream from the flow controlvalve 20 within the handle body 12 to control the temperature of themixed water flowing to an outlet passage 28. The thermostatic valve isdescribed in detail in PCT Publications WO 95/30940 and 95/30939 and isincorporated herein by reference.

The fixed ceramic disc plate 22 has respective cold and hot supply ports30 and 32 and a centrally located mixed water outlet port 34. Theceramic disc plate 24 is affixed to the rotatable handle body 12 via aninternal body member 36 of the cartridge assembly 25 for rotation withthe handle body 12. The movable ceramic disc plate 24 has a cold waterinlet 38 and hot water inlet 40 and a centrally located outlet aperture42 that is in constant alignment with outlet port 34 of fixed ceramicdisc plate 22. The rotation of the handle body 12 rotates the ceramicdisc plate 24 with respect to disc plate 22 selectively align ormisalign the inlet 38 and 40 with inlets 30 and 32 to control the totalflow rate of the hot and cold water. The handle body 12 may becircumscribed with a thermally insulating handle sleeve 27 thatfunctions as the handle.

The internal body member 36 has a hot water inlet passage 44 alignedwith the hot water inlet 40 and a cold water inlet passage 46 alignedwith the cold water inlet 42. A central mixed water outlet 43 is inalignment with outlets 42, 34 and 28. The passage 44 has an annularshaped downstream end 48 adjacent an annular valve seat 50 in internalbody member 36 and the axial lower end 52 of thermostatically controlledvalve 26 which is annular in shape. The passage 46 has an annular shapeddownstream end 54 adjacent an annular valve seat 56 and the axial upperend 58 of the annular shaped valve 26. Valve seat 56 is secured to theinternal body member 36. The passage 46 passes axially through theannular valve 26 within its radial confines. The internal body member 36has an intermediate seal seat 60 that seats a seal 62 that seals off thepassage 44 from 46 within the axial extent of the annular valve 26.

The annular valve 26 is affixed to a collar 64 via a threadedengagement. A spring 66 biases the valve 26 to engage the seat 56 andclose off passage 46. The collar 64 extends above the internal bodysection 36 and is operatively affixed to body section 68 of thermostaticelement 70. The thermostatic element has an expanding piston leg 72 thatengages a safety spring release seat 74 that is mounted in adjustmenthandle 76. The adjustment handle 76 is screwed onto handle body 12 withan appropriate seal 75 for mechanically raising and lowering thethermostatic assembly 70 within the cartridge assembly 25. The bodysection 68 may extend into the central outlet passage 42 of the internalbody 36.

The cartridge assembly 25 maintains its structural integrity because theannular valve 26 is entrapped between the internal body valve seat 50and the upper seat 56. The thermostatic element 70 is affixed to thecollar 64 which in turn is affixed to the annular valve 26. The springelement 66 is also entrapped between the internal body 36 and the valve26.

A retaining ring 82 which when it is inserted, firmly assembles theexternal body 12 of the device, the internal body 36 and the faucet basemember 17. The retaining ring 82 can be made from plastic material andmay conveniently be fixed with an elastic release. The plastic materialmay have a low coefficient of friction, so that the retaining ring 82also has the function of limiting friction when the thermostatic mixingvalve 10 is rotated to regulate the rate of flow. In this way the entirethermostatic mixing valve 10 assumes the character of a cartridge whichcan be installed and removed from the piping fixture 14 withoutentailing any disassembly of its parts. This same characteristic enablesthe entire device to be assembled independently of the inlet duringmanufacture, and the two parts to be stored separately in the warehouse.A locking ring 83 is then screwed into piping fixture 14 to mount thethermostatic valve 10 in place.

The water flow from the cold water supply 16 passes up through thecontrol valve 20 and axially upward through the internal body memberwith the cold water passing radially outward through the adjustablysized gap 78 between the seat 50 and annular valve 26 and into mixingchamber 80. The flow path from the hot water supply 18 passes throughthe control valve 20 and axially upward through the internal body memberwith the hot water passing radially outward through the adjustably sizedgap 79 between the seat 56 and annular valve 26 to mixing chamber 80.

The water thereafter is mixed and passes back radially inwardly to thecenter outlet passage 42 and out of the cartridge 25 and mixing valve10. The thermostatic adjustment automatically slides the valve 26axially to adjust the size of the two gaps 78 and 79. The specificinternal construction of the thermostatic element 70 is well known inthe art and is commercially available.

The volume control valve 20 when in the closed position prevents anycommunication between water supplies 16 and 18 and thus the faucet neednot be provided with non-return valves.

Reference now is made to FIGS. 2-6 for a more detailed description ofthe ceramic disc plates 22 and 24 and the shape and operation of theports 30 and 32 in the fixed plate 22 and inlets 38 and 40 in themovable plate. For ease of illustration, the two plates are shown, ashaving different diameters in FIGS. 4-6 but it is understood that thediameters of the respective plates are not critical to the invention andthey may have the same diameter.

These apertures 38 and 40 in movable plate 24 are shaped so as tosub-divide the entire field of regulation determined by the relativerotation of the plates into at least two distinct successive fields. Thefirst field of regulation, adjacent to the shut off position, isdetermined by at least one inlet passage aperture of narrow section,inserted in at least one of the pipes for hot water and cold water. Thesecond field of regulation is determined by inlet passage apertures oflarger flow section, inserted in both the hot water and cold waterpipes. It is not necessary to use inlet passage apertures having specialshapes in both valve plates. One of the valve plates, for example thefixed valve 22, illustrated in FIG. 2, can have, at the side of acentral passage aperture 34 for mixed water (which however may be absentin other forms of the embodiment), two inlet hot and cold passageapertures 30 and 32 having normal shape with an elongated curved slot.This is therefore effectively a valve plate of normal conventionalconstruction.

The characteristic structures of the invention however concern the othervalve plate, for example, the moveable valve plate 24. The passageapertures having a narrow section 85, which determine the first field ofregulation may be inserted into both the passages for hot water and coldwater, or alternatively, a single passage aperture with a narrow section85 may be inserted into a single pipe for hot water or for cold waterwith the other passage aperture not being narrowed at all. Embodimentsin which the passage apertures of narrow section which determine thefirst field of regulation are inserted into both the hot water and coldwater pipes are described with reference to FIGS. 3 to 12, while otherembodiments in which a single passage aperture having a narrow sectionis inserted into a single pipe for hot water or for cold water aredescribed with reference to FIGS. 13-16.

The valve plate 24, shown in the first embodiment in FIG. 3, has, at thesides of a central aperture 43 for mixed water two hot and cold passageapertures 38 and 40 made with wide sections 84 and narrow sections 85 todetermine the different fields of regulation of the valve. In this formof embodiment, narrow section 85 and wide section 84 each pass complete14 through the valve plate. FIGS. 4a, 4 b, 5 a, 5 b, 6 a and 6 b (inwhich for simplicity and clarity of the drawings, the central outletapertures 34 and 42 have been omitted) illustrate how these valve plates22 and 24 work together.

FIGS. 4a and 4 b respectively illustrate the moveable plate 24 and thefixed plate 22 in their relative shut off or closed positions. It willbe understood that when these valve plates are placed one above theother in this relative position, their inlet passage apertures,respectively 30, 32, 38 and 40 do not align and the flow of thethermostatic mixing valve is completely shut off.

If the moveable plate 24 is made to rotate to a position shown in FIG.5a, and it is placed against the fixed plate 22 as shown in FIG. 5b,only a greater or lesser part of the narrow sections 85 of the moveableplate 24 correspond to the respective inlet passage apertures 30 and 32of the fixed pate 22. The moveable plate 24 when in this positiondetermines a field of regulation for the thermostatic mixing valve inwhich the inlets of hot water and cold water are greatly restricted.Consequently, even if the delivered flow rate is reduced due to a highrestrictive delivery outlet, a significant drop in pressure occurs whenthe water passes through the inlet passage apertures of valve plates 22and 24, and the pressure inside the mixing chamber 80 of the valve isthen greatly reduced in relation to the pressures in the supply pipe.This significant drop in pressure at the inlet renders the valvepractically insensitive (for purposes of its stability) to differencesin pressure, even large ones, which may occur between the supply pipesthat may otherwise cause occurrences of instability. It is obvious onthe other hand that under these conditions the valve is not capable tosupply a plurality of devices which together require a high rate offlow. This field of regulation is suitable for supply to a single outletof a bank of multiple outlets.

If the moveable plate 24 is then made to rotate to a position like thatshown in FIG. 6a, and it is placed above the fixed plate 22 as shown inFIG. 6b, a greater or lesser part of the wide sections apertures 84 ofapertures 38 and 40 in the moveable plate 22 aligns with the inletpassage apertures 30 and 32 of the fixed plate 22. The moveable plate 22when in this position determines a field of regulation for thethermostatic mixing valve in which the inlets for hot water and coldwater are only slightly restricted and are operable for high flow rates.Consequently, in this field of regulation, the thermostatic mixing valveis capable of supplying several devices, or devices which require a highflow rate. This field of regulation suitable for the simultaneous supplyof a bank of multiple outlets.

The user can therefore set the thermostatic mixing valve to functionproperly in different conditions simply by rotating the body of thethermostatic mixing valve to a selection position. This rotating actioncorresponds to the normal action for regulating the flow rate of afaucet and is therefore easy and instinctive. It may be desirable toprovide signs or indicators on the visible parts of the thermostaticmixing valve to tell the user if the thermostatic mixing valve isoperating for low flow rates or for higher flow rates.

It would seem beneficial in any case to give the user a sensoryindication of passage from one field of regulation of the thermostaticmixing valve to another field, for example by means of an index releasesystem. An index mechanism between two relatively mobile parts of thethermostatic mixing valve can be provided. For example, in FIG. 1, inthe base 17 there is a ball 88 based by a spring 89, which workstogether with indentations 90 on the external body 12 of thethermostatic mixing valve 10, so as to produce detent stops which can beresiliently overridden which correspond to the passage from one field ofregulation to another. This device makes it easier for the users totactly determine the correct field of regulation for the thermostaticmixing valve.

It may be desirable to provide an intermediate field of regulation withan intermediate flow rate interposed between the field of regulationwith low flow rate and a field of regulation with a high flow rate. Insuch cases it may be necessary to shape the inlet apertures 30 and 32 ofthe moveable plate 24 as illustrated in FIG. 7. Aperture sections 86with an intermediate width between the widths of aperture sections 84and aperture sections 85 are interposed between the aperture sections 84and 85. In this case there are three fields of regulation of thethermostatic mixing valve instead of two.

Reference now is made to the embodiment illustrated in FIG. 8. The inletapertures 38 and 40 have wide areas 84 fully passing through plate 24.Stepped sections 87 do not pass completely through the plate 24 and haverelatively reduced depth. These stepped sections 87 act in the samefashion, as the narrow section 85 shown in FIG. 3. In fact, the flowwhich comes from apertures 30 and 32 of the fixed plate 22 runs intothese stepped sections 87, and is diverted towards the wide aperturesections 84. However, the flow is greatly restricted due to the limiteddepth of the stepped sections 87. Operation is therefore identical tothat described with reference to the form of embodiment in FIG. 3.However, mass production of the plate shown in FIG. 8, without thenarrow sections 85 may prove to be industrially more expeditious and itsstructure may be more durable.

Reference now is made to the embodiment illustrated in FIGS. 10 and 11which is constructed to give three fields of regulations. For thispurpose lies an intermediate stepped section 88 between the widecrossing apertures 84 and stepped section 87 limited depth. The depth ofstepped section 88 is greater than that of stepped section 87. Asexplained in relation to the preceding example, operation provesidentical to that of the form of embodiment shown in FIG. 7, havingthree aperture sections of different widths.

Reference now is made to the embodiment shown in FIG. 12 where thedesign criteria for the preceding forms of embodiment are combined. Inthis case, each inlet apertures 38 and 40 has a wide section 84 thatcompletely passes through plate 24. A narrow slot section 85 also fullypasses through plate 24. A stepped section 88 lies adjacent the slot 85and is of limited depth. It will be understood that this form ofembodiment performs in the same way as the forms of embodiment shown inFIGS. 7 and 10.

Reference now is made FIGS. 13-16 where other embodiments are describedfor the moveable valve plate 24 in which a single passage aperture ofhaving restricted field sections is inserted into a single pipe for hotwater or for cold water. The other passage aperture 40 does not havedirect restricted field sections.

The moveable valve plate shown in FIG. 13 is similar to the one alreadydescribed with reference to FIGS. 10 and 11 and it differs only in thefact that only one of its crossing passage apertures includes a widesection 84 and stepped sections 87 and 88. The other passage aperture onthe other hand includes only a conventional arcuate slot section whichfully passes through the valve plate. As we have already indicated, inthis case, when the valve is in its first field or regulation and onlyone water inlet, preferably for that of the cold water, is restricted,the reaction of the thermostatic system has the effect of reducing theadmission of water from the conventionally shaped inlet which does nothave the narrow restricted section. The desired result as previouslydescribed is therefore obtained in this case, not directly as a resultof the shape of both inlet passage apertures but due to the interventionof the thermostatic system.

The movable valve plate 24 shown in FIG. 14 is similar to that alreadydescribed with reference to FIG. 8, and differs from it only in the factthat only one of its passage apertures has a wide section 84 and astepped section 87 of reduced depth. The other passage aperture on theother hand includes only conventionally shaped wide section 84 whichpasses through plate 24. The desired result as previously described forFIG. 13 is also obtained in the case due to the intervention of thethermostatic system.

The movable valve plate shown in FIG. 15 is similar to the one alreadydescribed with reference to FIGS. 10 and 11 and it differs only in thefact that only one of its crossing passage apertures includes a widesection 84 and stepped sections 87 and 88. The other passage aperture onthe other hand includes a conventionally shaped wide section which fullypasses through the valve plate. As we have already indicated, in thiscase, when the valve is in its first field of regulation and only onewater inlet, preferably for that of the cold water, is restricted, thereaction of the thermostatic system has the effect of reducing theadmission of water from the conventionally shaped inlet which does nothave the restricted section. The desired results as previously describedis therefore obtained in this case, not directly as a result of theshape of both inlet passage apertures but due to the intervention of thethermostatic system.

The movable valve plate 24 shown in FIG. 16 is similar to that alreadydescribed with reference to FIG. 12 and differs from it only in the factthat only one of its passage apertures has a wide section 84, a narrowsection 85 and a stepped section 87 of reduced depth. The other passageaperture on the other hand includes only a conventionally shaped widesection 87 which passes through the valve plate. The desired results aspreviously described for is also FIG. 15 obtained in the case, due tothe intervention of the thermostatic system.

It must be understood that the invention is not limited to the forms ofembodiment described and illustrated as examples. Several modificationsbesides those already described are within the capability of a personqualified in the field. For example, the inlet passage apertures of thevalve plates may be shaped differently, provided that they form two ormore fields of regulation suitable for the delivery of very differentflow rates. The special shapes can be formed in the inlet passageapertures of the fixed valve plate, rather than of the moveable valveplate or they may involve both plates. Different methods from thosedescribed could be chosen to give the user a visual, tactile or othersensory warning of passage from one to another field of regulation.

In this fashion, a thermostatic valve for a mixing faucet is able tocorrect the temperature of the outlet water for more varieties ofplumbing conditions and water supplies. The invention increases theviability of thermostatic control valves where its mere action withoutthe inventive concept is not sufficient to maintain the outlet water atthe preselected or desired temperature.

Other variations and modifications are possible without departing fromthe scope and spirit of the present invention as defined by the appendedclaims.

I claim:
 1. A thermostatic mixing valve having a cold water inlet portand a hot water inlet port including: a base having two supply ports; arotatable handle body mounted onto said base and operably connected to afirst valving surface with a hot water and cold water inlet passagetherethrough that are operably positioned adjacent said two supply portsfor controlling volume flow into said housing; a thermostat elementoperably connected to a movable second valving surface that is movablebetween first and second seats for controlling the relative flow fromthe cold and hot water inlet passages in response to the temperature offluid in a mixing chamber; said ports and said first valving surfacebeing incorporated in two concentrically mounted plates that can berotated with respect to each other and provided with openingstherethrough for the controlled passage of the fluid through the twoplates; said thermostatic mixing valve characterized by: at least oneopening in one of said valve plates, is formed with two distinct fieldsso as to subdivide the entire field of regulation determined by therelative rotation of the plates into at least two successive fields, thefirst field of regulation, adjacent to the shut off position, beingdetermined by an inlet passage aperture first section of restricted flowand the second field of regulation, after the first, formed by anenlarged cross section; and a discrete third intermediate field ofregulation interposes between said first and second sections.
 2. Athermostatic mixing valve as defined in claim 1, further characterizedby: the opening is in the form of elongated slot and each offer aninitial length of reduced width forming said first section and a finallength of enlarged width forming said second section; and a discreteintermediate length of intermediate width between the first reducedwidth and second enlarged width of the first section widths of thesecond section.
 3. A thermostatic mixing valve as defined in claim 1further characterized by: the opening is in the form of an elongatedslot of large and uniform width, and having a first section fullyextending through the valve plate and a stepped section of limited depthnot fully passing through said valve plate; and the opening providedwith offer between the said crossing length and the said first derived,a intermediate section of greater depth that that of the stepped sectionbut not passing fully through said plate and interposed between saidfirst section and said stepped section.
 4. A thermostatic mixing valveas defined in claim 1 characterized by: the opening has a wide sectionfully extending through said plate and a stepped section of limiteddepth adjacent the narrow first section.
 5. A thermostatic mixing valvesas defined in claim 1 further characterized by: visible indicators aremounted on said thermostatic mixing valve which inform the user as towhich field of regulation the thermostatic mixing valve is operating in.6. A thermostatic mixing valve as defined in claim 1 furthercharacterized by: at least one elastic release device suitable forgiving a sensory warning to the user of the passage from one field toanother of regulation of the thermostatic mixing valve, said elasticrelease device being inserted between relatively moving parts of thethermostatic mixing valve.
 7. A thermostatic mixing valve as in claim 6further characterized by: said elastic release device comprises a springbiased ball that is seated in a first part of the body of thethermostatic mixing valve that can be biased into one or more cavitieswhich face it that are located in a second part of the body of thethermostatic mixing valve.